D-

The Internet bogeyman who actually inspired a couple of impressionable twelve-year old Wisconsin girls to attempt to kill a friend in 2014 comes to your favorite multiplex, but his appearance is more likely to engender hostility in you against the makers of “Slender Man” than toward anybody you know. There were more chills in a single frame of “The Babadook” than in this entire dreary movie.

Slender Man first showed up in 2009 on the website SomethingAwful.com in a post by one Eric Knudsen, aka Victor Surge. The spooky figure—a tall, dark, faceless creature with long, spindly fingers that was inserted into many contexts—became a popular web presence, often depicted as stalking and kidnapping children. From this foundation David Birke has contrived a plot about four high-school girls—Wren (Joey King), Hallie (Julia Goldani Telles), Chloe (Jaz Sinclair) and Katie (Annalise Basso)—who in effect summon up the fearsome fellow by uploading a video from the net—all it takes is Google, apparently—in which he appears. (Why? Because the guys are holding their own Slender Man party, girls not invited.) That apparently constitutes an invitation for him to come after them.

One says “apparently” because the rules about how Slender Man can operate are never made very clear, or to be more accurate, the movie seems to be making them up as it goes along. Not that it matters much, of course; the important thing is that the concept gives this creepy entity an opportunity to pursue the quartet of increasingly frantic girls, one by one. First Katie disappears on a school field trip, and then Chloe goes berserk. That leaves Wren and Hallie to try to get them back from the bogeyman that the former, after a bit of research, comes to believe is some sort of “bioelectrical” entity. But what is implied at the end of the movie is that whatever his makeup, he encases his victims in the trunks of trees, using branchlike tendrils to grab them up.

That, at least, is what seems to be happening, although “Slender Man” is so sloppily directed (by Sylvain White), murkily shot (by Luca Del Puppo) and haltingly edited (by Jake York) that it’s not always possible to discern what’s going on. There are lots of sequences that turn out to be hysterical nightmares, a couple of set pieces (one in a library, another in a hospital) that are creepily but pointlessly bizarre, and plenty of expository filler, much of it derived online from a chat room user named Alleeycat93, which one might not take to be a completely reliable source. There’s also a subplot involving a handsome jock (Alex Fitzalan) that literally goes nowhere, and another focused on Hallie’s younger sister (Taylor Richardson) that, as far as one can tell, makes no sense at all but does allow for the effects team to add a few more jump scares to the picture, accompanied of course but sudden bursts of noise on the soundtrack provided by Brandon Campbell and Ramin Djawadi.

As usual in such fare, the acting is pretty perfunctory. King and Telles have the most to do and go through their paces with grim determination, but in the end the basic function for all the girls is to scream a lot, a task they accomplish at a very high decibel level.

To be fair, the Slender Man figure could lend itself to some evocative images on screen, but here—especially when he turns into a human-like fellow played by Javier Botet, he looks rather silly (though not so ridiculous as the giant wooden spider he morphs into near the close). If you really want to be frightened by the emaciated giant, try to check out the 2017 HBO documentary “Beware the Slenderman,” which dealt with the 2014 Wisconsin case. It shows that the real horror lies not in the Internet-based Freddy Krueger clone Birke has created, but in the murderous impulse the original figure could instill in impressionable children. Now that’s scary in a way this cookie-cutter movie is not.